Neat, but rand might give the same result several times (as has already been pointed out), and you'll loose some lines, although that's unlikely. Here's how I'd do it anyway:

print sort { sprintf("%u",rand(2)) || -1 } <>;
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Explanations: rand(2) yields a float between 0 and 2 (2 excluded), sprintf returns the integer part, i.e. 0 or 1. If it's 0, take -1 instead. So the expression in curlies randomly returns 1 or -1, which causes the lines from <> to be randomly exchanged.

My € 0.02

btw, I'd be delight if someone could show me a better/shorter way than sprintf "%u" of getting the integer part of a float.

Update: of course, int (thanks mycocom)! I think I tried it once, but I must've messed up something, and I've been convinced that it didn't work ever since :-(